This invention relates to apparatus and methods for inhibiting excessive motion between selected moving components of a wave energy converter (WEC). Known wave energy converters (WECs) include two basic components which, when placed in a body of water, are designed to move relative to each other, in response to the motion of ocean (sea) waves. One of the two components may be denoted as a “float” (or shell) and the other one of the two components may be denoted as a central “column” (shaft or spar). A power take off (PTO) device is connected between the two components to convert their relative motion into electric energy.
A problem faced by the Applicants may be explained by referring to FIG. 1 and assuming that the float 10 moves up and down along the column 12 in response to the motion of the waves and by noting that the forces due to the waves may vary considerably. For example, the forces of the waves may be of such a magnitude (e.g., during a storm) that the travel of the float relative to the column may exceed a desired “operating range” and may, if not blocked, cause separation of the float from the column. That is, the float may become detached, or torn, from the column. It is therefore desirable and/or necessary to limit the travel of the float relative to the column to a predetermined operating range. It is desirable and/or necessary to limit movement beyond the operating range to reduce the possibility of excessive motion (and potential separation) which may occur due to the extreme forces frequently present (e.g., during a storm) in seas and oceans.
To avoid the problem, the prior art relies on various hydraulic and mechanical systems (e.g., springs and/or dampers) to stop and block excessive motion. An example of a prior art system using mechanical stops is shown in FIG. 1 which illustrates a mechanical damping system in which a power take off device (PTO) is connected between the shell 10 and a central column 12 and mechanical damping means 801a, 801b, 801c and 801d are used to prevent the shell 10 from going above a certain level relative to shafthead 803 and from going below a certain level relative to the shafthead. In this type of system, there may be excessive forces applied to the stops 801a, b, c, and d. Reliance on mechanical stops and/or dampers is generally not satisfactory because of the cost and because they are subject to wear and breakdowns due to the forces applied to them. Stops and/or dampers are shown in FIG. 1, but a similar problem exists with hydraulic and/or other mechanical systems.